Microsoft has pulled a build of its Windows 10 Technical Preview for several low-end Lumia phones after reports some devices in its early tester program had been bricked.

Lumia device owners testing one build of the Windows 10 Technical preview found their phones unusable after attempting to roll back to Windows Phone 8.1.

A Microsoft employee announced on the Windows Insider Program discussion board this week that due to the reports of bricked handsets, it was suspending the preview build for the Lumia 520, 525, and 526 - some of Microsoft's cheapest and best-selling Lumia models.

"We are seeing some reports of failures on Lumia 520/525/526 devices when trying to roll back to Windows Phone 8.1 using the Windows Phone Recovery Tool. We are pausing build availability for these devices temporarily while we investigate the issue and work with customers who have reported problems," the Microsoft employee said.

The Windows Insider program allows anyone with a bit of technical knowledge to try out Microsoft's work-in-progress OS and provide feedback and help shape the final product. The company has about one million registered insiders that can opt for either Fast builds, which are less stable, or Slow for the risk-averse.

The build that has caused problems for the Lumia devices, 10051, was released last week in the Fast lane. As such, insiders were warned to expect a number of known issues, and Microsoft offered its Windows Phone Recover Tool as a way to remedy those problems.

So, for Lumia 520 owners the safer way for them to currently see what's in store for Windows 10 mobile will be to check out ZDNet's first look at key feature updates in 10051, such as new notifications and the updated Outlook app.

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